1. Field of the Invention
This invention relates to devices for securing the male and female plugs of an electric cord together to avoid inadvertent separation when tension is applied to the cord. More specifically, the subject invention relates to a device for securing the female end of an extension cord to the plug of an electric cord, such as might be used for various items of movable electrical equipment.
2. Prior Art
It is not infrequent that a piece of electrical equipment, such as a drill, rotary saw, electrical garden clippers, etc., must be attached to an extension cord in order to operate at a desired location. In such circumstances, the attachment of the electrical device by its own cord to the extension cord is accomplished by merely inserting the male plug of the electrical device into the female plug of the extension cord. This arrangement is satisfactory as long as the electrical cord is not pulled free from the extension cord while the equipment is being moved from one location to another.
During such movement, it is a frustrating experience for the worker to be constantly on the move, only to pull the male plug free from the extension cord. The resulting need to reinstall the extension cord to the electrical device results in a waste of time, as well as the aggravation which normally accompanies the experience.
Several devices have been developed in an attempt to deal with the problem of cord separation. For example, U.S. Pat. No. 4,221,449 by Shugart, Jr. discloses a locking device comprising a longitudinal bar having a portion of its surface serrated, a fixed end member secured to one end of the bar and an adjustable moving locking member slidably mounted on the opposing end of the bar. The plug and socket to be secured are connected at the respective ends of the device to form a binding engagement which prevents the plugs from being separated. Although the device works in circumstances where the pulling force is applied along the longitudinal axis of the joined plugs, it fails to provide a sure locking engagement where the plug is pulled around a corner or along an arcuate path. In such circumstances, the plug is pulled free from the securing clips or members and is thereupon subject to separation.
A similar arrangement is shown in U.S. Pat. No. 4,145,105 by Dobson. This configuration comprises a first and second section, wherein the first section has a conically-shaped plug receptacle adapted to receive any of a plurality of different sized electrical plugs, and a detent slot for holding the cord affixed to the plug. The second section has a detent slot adapted to receive a second electrical cord. The two parts are joined by an adjustable means which connects the first and second sections. Although this configuration has some advantages over the earlier cited prior art, this latter device is somewhat cumbersome because it is comprised of two separate pieces. Not only are such pieces subject to being separated and lost, but the application of this device to a cord generally requires two hands in order to successfully secure the plugs together. Finally, its secured position is not totally immune from inadvertent separation, particularly where the cord is pulled around corners or the like.
U.S. Pat. No. 4,097,105 shows another device for harnessing connected plugs. The harness includes a primary ring-like member from which a pair of elongate connectors extend in perpendicular fashion. A second ring-like member is adjustably coupled to the elongate connectors to permit harness installation on a variety of plug/socket combinations. Although the harness provides a secure means of attachment, the configuration is cumbersome and awkward because of the numerous pieces involved, which may become separated and lost. Likewise, with a greater number of pieces to attach, both hands are needed to couple the harness to the connected plugs. Also, because of the numerous connecting joints, there is a greater tendency for the harness to break free under extreme twisting or extension.
Earlier prior art designs, considered to be less pertinent than those references cited above, include U.S. Pat. Nos. 3,475,716 by Laig; 2,461,427 by Kneebone; and 2,406,567 by Schueneman. The devices disclosed in these earlier patents conform to the structural types as disclosed above, and also carry the disadvantages previously referenced.